Northwest Africa 6601 (NWA 6601)

Morocco

Found: October 2010

Classification: HED achondrite (Eucrite)

History: Found near Mhamid, Morocco, in October 2010. Purchased in Tucson, AZ, in January 2011 by Thompson.

Physical characteristics: Three fragments that fit together into one mass of 276.2 g. Light-gray exterior with minor iron staining. Interior shows light-gray matrix crosscut by numerous dark-gray veins to 3 mm. Metal grains visible.

Petrography: (C. Agee, UNM). Thin sections reveals low- and high-Ca pyroxene (~60%) and plagioclase feldspar (30%), with silica, Cr-spinel, ilmenite, troilite, and Fe-metal; olivine absent. Pyroxene and plagioclase to 500 μm. Some areas resemble fine-grained cataclastite. Pyroxene shows exsolution lamellae and planar parting, fracturing, and microfaulting. Some plagioclase as large laths, some transitioning into impact melt. Equant to irregular Fe-metal grains to 300 μm. Troilite commonly fine grained. Numerous impact melt veins and pockets to 500 μm, containing abundant silica, troilite and rafted basaltic clasts.

Geochemistry: (C. Agee and M. Spilde, UNM) Equilibrated, brecciated, main group eucrite permeated with shock melt. Orthopyroxene Fs_61.2±0.9Wo_3.7±1.0, Fe/Mn=29 ± 1, n=7, clinopyroxene Fs_26.6±1.0Wo_44.5±0.8, Fe/Mn=30 ± 2, n=4, plagioclase Or_0.5Ab_10.1An_89.4, shock melt veins SiO₂ = 48.2 ± 1.6 wt%, CaO/Al₂O₃ (wt%)=0.64, Mg# = 0.37 ± 0.01, TiO₂ = 0.61 ± 0.37 wt%, n=7. Metal Ni<0.01 wt% Co=0.04 ± 0.02 wt%, n=5.

Classification: Achondrite (eucrite); low weathering grade, high shock grade, numerous impact melt veins and pools present.

Specimens: Thompson holds the main mass, type specimen of 22 g on deposit at UNM.